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Code Issues Releases Activity

Fixed: Performance of symbolic link detection and infinite recursion

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This commit is contained in:
Taloth Saldono 2020-06-14 02:05:56 +02:00
parent 1509e737c2
commit f56003e288
2 changed files with 148 additions and 35 deletions
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64
src/NzbDrone.Mono.Test/DiskProviderTests/SymlinkResolverFixture.cs Normal file
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@ -0,0 +1,64 @@
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using FluentAssertions;
using Mono.Posix;
using Mono.Unix;
using NUnit.Framework;
using NzbDrone.Mono.Disk;
using NzbDrone.Test.Common;
namespace NzbDrone.Mono.Test.DiskProviderTests
{
[TestFixture]
[Platform("Mono")]
public class SymbolicLinkResolverFixture : TestBase<SymbolicLinkResolver>
{
public SymbolicLinkResolverFixture()
{
MonoOnly();
}
[Test]
public void should_follow_nested_symlinks()
{
var rootDir = GetTempFilePath();
var tempDir1 = Path.Combine(rootDir, "dir1");
var tempDir2 = Path.Combine(rootDir, "dir2");
var subDir1 = Path.Combine(tempDir1, "subdir1");
var file1 = Path.Combine(tempDir2, "file1");
var file2 = Path.Combine(tempDir2, "file2");
Directory.CreateDirectory(tempDir1);
Directory.CreateDirectory(tempDir2);
File.WriteAllText(file2, "test");
new UnixSymbolicLinkInfo(subDir1).CreateSymbolicLinkTo("../dir2");
new UnixSymbolicLinkInfo(file1).CreateSymbolicLinkTo("file2");
var realPath = Subject.GetCompleteRealPath(Path.Combine(subDir1, "file1"));
realPath.Should().Be(file2);
}
[Test]
public void should_throw_on_infinite_loop()
{
var rootDir = GetTempFilePath();
var tempDir1 = Path.Combine(rootDir, "dir1");
var subDir1 = Path.Combine(tempDir1, "subdir1");
var file1 = Path.Combine(tempDir1, "file1");
Directory.CreateDirectory(tempDir1);
new UnixSymbolicLinkInfo(subDir1).CreateSymbolicLinkTo("../../dir1/subdir1/baddir");
var realPath = Subject.GetCompleteRealPath(file1);
realPath.Should().Be(file1);
}
}
}

119
src/NzbDrone.Mono/Disk/SymbolicLinkResolver.cs
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@ -1,4 +1,6 @@
using System;
using System.Drawing;
using System.Net;
using System.Text;
using Mono.Unix;
using Mono.Unix.Native;
@ -11,8 +13,6 @@ public interface ISymbolicLinkResolver
string GetCompleteRealPath(string path);
}
// Mono's own implementation doesn't handle exceptions very well.
// All of this code was copied from mono with minor changes.
public class SymbolicLinkResolver : ISymbolicLinkResolver
{
private readonly Logger _logger;
@ -28,34 +28,27 @@ public string GetCompleteRealPath(string path)
try
{
string[] dirs;
int lastIndex;
GetPathComponents(path, out dirs, out lastIndex);
var realPath = path;
for (var links = 0; links < 32; links++)
{
var wasSymLink = TryFollowFirstSymbolicLink(ref realPath);
if (!wasSymLink)
{
return realPath;
}
}
var realPath = new StringBuilder();
if (dirs.Length > 0)
{
var dir = UnixPath.IsPathRooted(path) ? "/" : "";
dir += dirs[0];
realPath.Append(GetRealPath(dir));
}
for (var i = 1; i < lastIndex; ++i)
{
realPath.Append("/").Append(dirs[i]);
var realSubPath = GetRealPath(realPath.ToString());
realPath.Remove(0, realPath.Length);
realPath.Append(realSubPath);
}
return realPath.ToString();
var ex = new UnixIOException(Errno.ELOOP);
_logger.Warn("Failed to check for symlinks in the path {0}: {1}", path, ex.Message);
return path;
}
catch (Exception ex)
{
_logger.Debug(ex, string.Format("Failed to check for symlinks in the path {0}", path));
_logger.Debug(ex, "Failed to check for symlinks in the path {0}", path);
return path;
}
}
private static void GetPathComponents(string path, out string[] components, out int lastIndex)
{
var dirs = path.Split(UnixPath.DirectorySeparatorChar);
@ -87,23 +80,77 @@ private static void GetPathComponents(string path, out string[] components, out
lastIndex = target;
}
public string GetRealPath(string path)
private bool TryFollowFirstSymbolicLink(ref string path)
{
do
string[] dirs;
int lastIndex;
GetPathComponents(path, out dirs, out lastIndex);
if (lastIndex == 0)
{
var link = UnixPath.TryReadLink(path);
return false;
}
if (link == null)
var realPath = "";
for (var i = 0; i < lastIndex; ++i)
{
if (i != 0 || UnixPath.IsPathRooted(path))
{
var errno = Stdlib.GetLastError();
if (errno != Errno.EINVAL)
{
_logger.Trace("Checking path {0} for symlink returned error {1}, assuming it's not a symlink.", path, errno);
}
return path;
realPath = string.Concat(realPath, UnixPath.DirectorySeparatorChar, dirs[i]);
}
else
{
realPath = string.Concat(realPath, dirs[i]);
}
var pathValid = TryFollowSymbolicLink(ref realPath, out var wasSymLink);
if (!pathValid || wasSymLink)
{
// If the path does not exist, or it was a symlink then we need to concat the remaining dir components and start over (or return)
var count = lastIndex - i - 1;
if (count > 0)
{
realPath = string.Concat(realPath, UnixPath.DirectorySeparatorChar, string.Join(UnixPath.DirectorySeparatorChar.ToString(), dirs, i + 1, lastIndex - i - 1));
}
path = realPath;
return pathValid;
}
}
return false;
}
private bool TryFollowSymbolicLink(ref string path, out bool wasSymLink)
{
if (!UnixFileSystemInfo.TryGetFileSystemEntry(path, out var fsentry) || !fsentry.Exists)
{
wasSymLink = false;
return false;
}
if (!fsentry.IsSymbolicLink)
{
wasSymLink = false;
return true;
}
var link = UnixPath.TryReadLink(path);
if (link == null)
{
var errno = Stdlib.GetLastError();
if (errno != Errno.EINVAL)
{
_logger.Trace("Checking path {0} for symlink returned error {1}, assuming it's not a symlink.", path, errno);
}
wasSymLink = true;
return false;
}
else
{
if (UnixPath.IsPathRooted(link))
{
path = link;
@ -113,8 +160,10 @@ public string GetRealPath(string path)
path = UnixPath.GetDirectoryName(path) + UnixPath.DirectorySeparatorChar + link;
path = UnixPath.GetCanonicalPath(path);
}
} while (true);
}
wasSymLink = true;
return true;
}
}
}
}